Being a European first, I am not surprised. At soccer games in Europe it gets pretty nasty. Drunk stupid people often equal violence in my opinion.
In Vancouver's case, I am sure the Black Bloc were involved. Little anarchist kids, running around with bats and Molotov cocktails. I have been to countless demonstrations and once you see them a couple of times in action, it's pretty easy to spot them.
The police failed miserably though, just like they did at the G 20 in Toronto, after spending two billion dollars (well, it wasn't all spent in Toronto but Toronto was called Fortress City and cop cars still went-up in flames). Rather pathetic ...
The riot in Vancouver wasn't about sports, in my opinion.